The invention is based on a permanent magnet and an electric machine comprising such a permanent magnet, and a method for producing the electric machine.
EP 0 430 198 B1 has disclosed a sintered rare earth permanent magnet having a coating film composed of a corrosion- and oxidation-resistant material. In this case, the coating film is applied to the permanent magnet for example by electrolytic coating or by means of electroless plating.
When such a permanent magnet is incorporated, for example into an electric machine, contact of the surface coating of the permanent magnet with a more electropositive metal in accordance with the electrochemical series can lead to oxidation of the metal constituents of the coating. As a result, the anticorrosion protective layer is damaged, as a result of which the material of the permanent magnet reacts electrochemically directly with the more electropositive metal of the surroundings. As a result, undesirable corrosion of the magnet material occurs in specific ambient conditions. Consequently, specific areas of use of such a rare earth magnet are ruled out.